I always consider Diamond Tiara as less a spoiled brat and more a young, pint-sized, female pony Palpatine, who's going to grow up to become a potential evil overlord or super villainess, gunning for World domination. She shares a lot of similarities with young Palpatine, too, with the exception of Force powers, an abusive parent and a Sith Lord mentor like Darth Plagueis.

(Well, that just gave me an idea for a FIM story...)

She would definitely want to become an Alicorn, though, and I suspect it'll involve a truly diabolic scheme...

Well I do have a bit of a headcannon about her past but Babs will be on the list

Diamond Tiara's background.Diamond Tiara, before her cutie mark, was eagerly seeking her own answers…

"Who am I? What am I ment to do?" She’d constantly ask her dad. She had friends too… her fellow "Blank Flanks" which included a filly with poor eyesight and a pearl necklace. The only one she told why she held onto that was Tiara herself.

"It was the last thing mother gave me before leaving on a diplomatic errend to the Gryphon Kingdom. There she was assassinated" She told her in private once and in tears. Since her diplomatic father had died of cancer a few months before as well Filthy Rich adopted her.

She also had a small pegasus friend with green fur and a yellow mane, a unicorn with a purple mane and red body as well… Then the “Fillies Pagent”…

Reading the pamplet they all decided to enter. “We could definately get our cutie marks here, look they have many things for us to try” Diamond Tiara stated eagerly.

Silverspoon nodded in agreement as did the others… preparing both of them for the pagent Filthy Rich helped train them.

The pagent came and went, with a narrow margin Diamond Tiara was awarded the Tiara, the symbol of the pagent winner.

With a bright flash a tiara appeared on her flank as well. “MY CUTIE MARK!!!” She exclaimed with a smile as Silverspoon hugged her…

however her other friends distained her. “You’re big talent is winning a pagent, how lame!” one would taunt “It’s pathetic and you’re pathetic” Another added.

Just outside of the building her former friends booed her and threw rotten produce at her. However Silverspoon stood up “HOW DARE YOU!?!” She exclaimed

"She’s pathetic, her only talent is wearing that damn tiara" One taunted…

From the pegasus… those words cut into Diamond Tiara’s heart and she walked away, rotten tomato dripping from her mane and into her eyes.

"If she’s so pathetic then how did she beat all of you? You’re just jealous" Silverspoon retorted, finding herself disgusted at the sudden hatrid for Tiara her so called "friends" had.

Silverspoon started to walk away but one of them yelled “YOU’RE JUST AS PATHETIC!” when she glared at them “I dont talk to those who’s minds are as blank as their flanks” She retorted with anger.

Back at the house Diamond Tiara fell ill… the illness brought on by the rotten food tossed her way.

Silverspoon prepared her a special soup from a recipe her mother taught her in life. Using a spoon she helped feed the extremely sickly Diamond Tiara.

Without her noticing Silverspoon gained her cutie mark of a spoon while she was feeding Diamond Tiara… “T..They betrayed us…” Was all Diamond tiara could say.

Her heart growing cold… she hated how a group of Blank Flanks stabbed her in the heart…

she hated her own cutie mark, she felt it was responsible for her situation…

"this…" Silverspoon was about to refer to herself as a "Blank Flank" but she noticed she had her cutie mark.